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Bench Mark Sheet for 9450970, Thoms Point AK

Superseded Epoch

Large map location marker Station Location
Small red map location marker Published bench mark
Small blue map location marker Unpublished bench mark

Bench mark positions only appear on the map if their coordinates in the CO-OPS database are at the precision of degrees/minutes/seconds/and tenths of seconds. If the coordinates are less precise, the mark will not appear.

Printable version

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  5

                                                                                
Station ID: 9450970                         PUBLICATION DATE:  08/05/2005
Name:       THOMS POINT, ZIMOVIA STRAIT                       
            AK
NOAA Chart: 17385                           Latitude:   56°  7.1' N (  56.11830)
USGS Quad:  PETERSBURG (A-1)                Longitude: 132°  4.7' W (-132.07800)


To reach the tidal marks from Wrangell via boat, proceed 26.3 km (14.3 nm) south
from Wrangell Harbor through Zimovia Strait until abeam of Anita Point.  Then
proceed 21.5 km (11.7 nm) SE through Zimovia Strait until abeam of Thoms Point
located north of the north tip of Frost Island, on the southernmost tip of
Wrangell Island.  Then proceed 1.1 km (0.6 nm) NW of the southernmost extent of
Wrangell Island.  The bench marks, staff, and tide gauge were located on the
beach in the vicinity.


                         T I D A L   B E N C H   M A R K S


                 PRIMARY BENCH MARK STAMPING:  0970 E 2001
                         DESIGNATION:          945 0970 E

MONUMENTATION:           Tidal Station disk                    VM#:        16490
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Rock outcrop                          OPUS PID:        
LATITUDE:   56°  7.1' N (  56.11830)          LONGITUDE: 132°  4.7' W (-132.07800)


The primary bench mark is a disk set flush in a bedrock outcrop, 31 m (102 ft)
NNW of the seaward most extent of the point of land just west of the
southern-most extent of Thoms Point, 20.51 m (67.3 ft) SE of a clearing that
extends from the west to the south shore of the point, 14.50 m (47.6 ft) NW (345
degrees magnetic) from bench mark 0970 D 2001, 12.30 m (40.4 ft) east of the
vegetation line, and 6.50 m (21.3 ft) north of a 3 m x 3 m (10 ft x 10 ft)
triangular granite rock.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  5

                                                                                
Station ID: 9450970                         PUBLICATION DATE:  08/05/2005
Name:       THOMS POINT, ZIMOVIA STRAIT                       
            AK
NOAA Chart: 17385                           Latitude:   56°  7.1' N (  56.11830)
USGS Quad:  PETERSBURG (A-1)                Longitude: 132°  4.7' W (-132.07800)


                         T I D A L   B E N C H   M A R K S


                         BENCH MARK STAMPING:  0970 A 2001
                         DESIGNATION:          945 0970 A

MONUMENTATION:           Tidal Station disk                    VM#:        16486
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Rock outcrop                          OPUS PID:        
LATITUDE:   56°  7.1' N (  56.11830)          LONGITUDE: 132°  4.7' W (-132.07800)


The bench mark is a disk set flush in a black bedrock outcrop with intrusions of
quartz, located on Thoms Point, approximately 355 m (1,165 ft) NW from the
southern-most tip of Wrangell Island, NW (319 degrees magnetic) of the west
extent of Found Island, and WNW (293 degrees magnetic) of the east extent of
Found Island, 15.60 m (51.2 ft) WNW (293 degrees magnetic) from bench mark 0970
B 2001, and 8 m (26 ft) seaward of the vegetation line.



                         BENCH MARK STAMPING:  0970 B 2001
                         DESIGNATION:          945 0970 B

MONUMENTATION:           Tidal Station disk                    VM#:        16487
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Rock outcrop                          OPUS PID:        
LATITUDE:   56°  7.1' N (  56.11830)          LONGITUDE: 132°  4.7' W (-132.07800)


The bench mark is a disk set flush in a black bedrock located on the SW extent
of Thoms Point, approximately 350 m (1,148 ft) NW (264 degrees magnetic) of the
southern-most extent of Thoms Point, SE (140 degrees magnetic) from a day marker
located on the west side of Found Island, ESE (113 degrees magnetic) from the
east extent of Found Island, 15.6 m (51.2 ft) ESE (113 degrees magnetic) from
bench mark 0970 A 2001, 10 m (33 ft) seaward from the vegetation line, and 4 m
(13 ft) shoreward of the apparent high water line.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  5

                                                                                
Station ID: 9450970                         PUBLICATION DATE:  08/05/2005
Name:       THOMS POINT, ZIMOVIA STRAIT                       
            AK
NOAA Chart: 17385                           Latitude:   56°  7.1' N (  56.11830)
USGS Quad:  PETERSBURG (A-1)                Longitude: 132°  4.7' W (-132.07800)


                         T I D A L   B E N C H   M A R K S


                         BENCH MARK STAMPING:  0970 C 2001
                         DESIGNATION:          945 0970 C

MONUMENTATION:           Tidal Station disk                    VM#:        16488
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Rock outcrop                          OPUS PID:        
LATITUDE:   56°  7.1' N (  56.11830)          LONGITUDE: 132°  4.7' W (-132.07800)


The bench mark is a disk set flush in a bedrock outcrop located on the SW extent
of Thoms Point, 330 m (1,083 ft) NW  (264 degrees magnetic) of the southern-most
extent of Thoms Point, 19 m (63 ft) seaward of the vegetation line, 13.01 m
(42.7 ft) ESE (109 degress magnetic) of bench mark 0970 A 2001, and 13.01 m
(42.7 ft) south (175 degrees magnetic) from bench mark 0970 D 2001.



                         BENCH MARK STAMPING:  0970 D 2001
                         DESIGNATION:          945 0970 D

MONUMENTATION:           Tidal Station disk                    VM#:        16489
AGENCY:                  National Ocean Service (NOS)          IDB PID#:        
SETTING CLASSIFICATION:  Rock outcrop                          OPUS PID:        
LATITUDE:   56°  7.1' N (  56.11830)          LONGITUDE: 132°  4.7' W (-132.07800)


The bench mark is a disk set flush in a bedrock outcrop, located approximately
325 m (1,066 ft) WNW  (268 degrees magnetic) of the southern-most extent of
Thoms Point, 14.51 m (47.6 ft) SSW (165 degrees magnetic) from bench mark 0970 E
2001, 13.01 m (42.7 ft) north (355 degrees magnetic) of bench mark 0970 C 2001,
and 11.50 m (37.7 ft) seaward of the vegetation line.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  5

                                                                                
Station ID: 9450970                         PUBLICATION DATE:  08/05/2005
Name:       THOMS POINT, ZIMOVIA STRAIT                       
            AK
NOAA Chart: 17385                           Latitude:   56°  7.1' N (  56.11830)
USGS Quad:  PETERSBURG (A-1)                Longitude: 132°  4.7' W (-132.07800)


                            T I D A L   D A T U M S 


Tidal datums at THOMS POINT, ZIMOVIA STRAIT based on:

     LENGTH OF SERIES:      1 MONTH
     TIME PERIOD:           April 2001 - May 2001
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:  9450460 KETCHIKAN, TONGASS NARROWS


Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:

     MEAN HIGHER HIGH WATER                     MHHW   =  4.978
     MEAN HIGH WATER                            MHW    =  4.710
     MEAN TIDE LEVEL                            MTL    =  2.592
     MEAN SEA LEVEL                             MSL    =  2.590
     MEAN LOW WATER                             MLW    =  0.474
     MEAN LOWER LOW WATER                       MLLW   =  0.000

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     0970 E 2001                                 5.391    0.682
     0970 A 2001                                 4.564   -0.146
     0970 B 2001                                 5.405    0.695
     0970 C 2001                                 4.330   -0.379
     0970 D 2001                                 5.541    0.831


                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  5 of  5

                                                                                
Station ID: 9450970                         PUBLICATION DATE:  08/05/2005
Name:       THOMS POINT, ZIMOVIA STRAIT                       
            AK
NOAA Chart: 17385                           Latitude:   56°  7.1' N (  56.11830)
USGS Quad:  PETERSBURG (A-1)                Longitude: 132°  4.7' W (-132.07800)


                             D E F I N I T I O N S


Mean Sea Level (MSL) is a tidal datum determined over a 19-year National Tidal
Datum Epoch.  It pertains to local mean sea level and should not be confused
with the fixed datums of North American Vertical Datum of 1988 (NAVD88).

NAVD88 is a fixed datum derived from a simultaneous, least squares, minimum
constraint adjustment of Canadian/Mexican/United States leveling observations.
Local mean sea level observed at Father Point/Rimouski, Canada was held fixed as
the single initial constraint.  NAVD88 replaces NGVD29 as the national
standard geodetic reference for heights.  Bench mark elevations relative to
NAVD88 are available from NGS through the World Wide Web at 
National Geodetic Survey.

NGVD29 is a fixed datum adopted as a national standard geodetic reference for
heights but is now considered superseded.  NGVD29 is sometimes referred to as
Sea Level Datum of 1929 or as Mean Sea Level on some early issues of Geological
Survey Topographic Quads.  NGVD29 was originally derived from a general
adjustment of the first-order leveling networks of the U.S. and Canada after
holding mean sea level observed at 26 long term tide stations as fixed.
Numerous local and wide-spread adjustments have been made since establishment in
1929.  Bench mark elevations relative to NGVD29 are available from the National
Geodetic Survey (NGS) data base via the World Wide Web at 
National Geodetic Survey.

NAVD88 and NGVD29 are fixed geodetic datums whose elevation relationships to
local MSL and other tidal datums may not be consistent from one location to
another.

The Vertical Mark Number (VM#) and PID# shown on the bench mark sheet are unique
identifiers for bench marks in the tidal and geodetic databases, respectively.
Each bench mark in either database has a single, unique VM# and/or PID# assigned.
Where both VM# and PID# are indicated, both tidal and geodetic elevations are
available for the bench mark listed. The NGS's Integrated Data Base (IDB PID)
provides geodetic datum based on traditionally leveled and bluebooked ties to
the National Spatial Reference System(NSRS) https://www.ngs.noaa.gov/datasheets/.
The NGS Online Positioning User Service (OPUS PID) provides geodetic datum based
on GPS position & tie it to the NSRS https://www.ngs.noaa.gov/OPUS/.

The NAVD88 elevation is shown on the Elevations of Tidal Datums Table Referred
to MLLW only when two or more of the bench marks listed have NAVD88 elevations.
The NAVD88 elevation relationship shown in the table is derived from an average
of several bench mark elevations relative to tide station datum.  As a result of
this averaging, NAVD88 bench mark elevations computed indirectly from the tidal
datums elevation table may differ slightly from NAVD88 elevations listed for
each bench mark in the NGS database.

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Products available at 9450970 Thoms Point, AK

Revised: 10/15/2013
NOAA / National Ocean Service
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